One of the fundamental issues in designing a telecommunications network is how to ensure that the nodes in the network are temporally synchronized. If the nodes are not synchronized, communication across the network can be impossible or inefficient, and, therefore, it is essential to ensure that the nodes are synchronized.
In accordance with one technique in the prior art, one node in a network is designated as the “master” node and all of the remaining nodes are, by implication, designated as “non-master” nodes. In accordance with this technique, all of the non-master nodes in the network are synchronized by the master node that transmits a master timing signal to every non-master node, which conforms its own timing to that of the master timing signal. One disadvantage of this technique is that the operation of the entire network relies solely on the integrity of the master node and the master timing signal and if a problem occurs with either the master node or the master timing signal, then the entire network can fail.
In accordance with a second technique in the prior art, two or more nodes in a network are designated as “master” nodes and all of the remaining nodes are, by implication, designated as “nonmaster” nodes. In accordance with this technique, each master node transmits a master timing signal to every other node. Each master node synchronizes its own timing with that of the timing signals it receives from the other master nodes, and each non-master node conforms its own timing to that of the average of all of the master timing signals that it receives.
One advantage of the second technique is that the operation of the entire network does not rely solely on the integrity of a single node, and, therefore, if all but one of the master nodes incurs a failure, the network might survive. One disadvantage of the second technique, however, involves the issue of how each node arbitrates between the respective, and undoubtedly disparate master timing signals. A second, theoretically similar disadvantage of the second technique involves the issue of how each node determines when a master node is malfunctioning and that its master timing signal should be ignored or discounted. A third disadvantage of the second technique involves the issue of how to ensure that each node receives the master timing signal transmitted from each master node. This is of particular importance in wireless networks in which not all of the nodes can necessarily receive a direct transmission from every other node.
In accordance with a third technique in the prior art, each node in a network transmits a timing signal to every other node in the network, and, in such cases, each node conforms its own timing to that of the average of all of the timing signals that it receives. One disadvantage of the third technique is that because of the averaging there are inherent temporal delays in the propagation of timing signals, and, therefore there is inherently feedback in the system. Depending on the topology of the network and other technical factors, this feedback could cause the network timing to become unstable, which might cause the network to fail.
In accordance with a fourth technique in the prior art, each node in a network comprises a satellite positioning system receiver (e.g., a Global Positioning System or “GPS” receiver) and each node conforms its own timing to that of the satellite positioning system. One advantage with the fourth technique is that there is no feedback in the system, and, therefore, the network timing is stable. One disadvantage with the fourth technique is that, in some applications, it can be prohibitively expensive to include a satellite positioning system receiver with each node.
Therefore, the need exists for a technique for temporally synchronizing the nodes in a telecommunications network.